Flash butt welding is a technique for joining lengths of metal that are aligned end to end and then are electronically charged, producing an electric arc that melts and welds the ends of the segments, yielding a joined connection. The ends of the material are upset during the melt stage of the process thereby expelling most of the melted material from the interface. This produces a “flash” around an interface of solidified metal.
Heating and melting changes the microstructure and properties of the material at the interface. In addition to the weld area, a heat-affected zone (HAZ) is formed adjacent the weld. The heat-affected zone is the area of base material that is not melted during the welding process, but which has had its microstructure and properties altered by the welding operation. While butt welding typically provides an annealing cycle to soften the HAZ, it cannot restore the material to its original condition. Moreover, the additional steps introduce extra time, cost and complexity to the process. Therefore the HAZ will not perform like the bulk material and therefore typically needs to be tagged and removed to avoid damage to post processing operations.